Certain ester acids and certain ester salts of sulfoaromatic fatty acids, and method of making same



States Melvin De Groote, University City, Mo., assignor to Petrolite Corporation, a corporation of Delaware No Drawing. Application May 27, 1950 Serial No. 164,858

. 34 Claims. or. 260-402 Unite The pesent invention is concerned with certain ester acids and certain ester salts of sulfoaromatic fatty acids, and a method for making the same. Both types of compounds, i. e., the ester acids and the ester salts, are characterized by the presence of the radical (CaHeO)1tH in which n is a whole number varying from 10 to 60. Similarly, both types of compounds are characterized by being essentially hydrophobic in property.

The present invention is concerned with a four-fold objective: i

(a) The ester salt of a sulfoaryl fatty acid of the following structure:

said sulfoaryl fatty acid being an addition product of a monoethylenic higher fatty acid of the structure:

R-C=CRCOOH in which R is the monovalent hydrocarbon radical having a terminal methyl radical and connected with the ethylenic linkage, and R is the divalent hydrocarbon radical connecting the ethylenic linkage with the carboxyl radical; R is an aryl group having not more than 25 carbon atoms 71 being a Whole number varying from 10 to 60; and with the further proviso that the sodium salt:

is predominantly hydrophobe in character, and the corresponding methyl ester of the sodium salt:

RSOa.Na H l R-O- ROOOCH2 H H is water-soluble and predominantly hydrophile:

(b) The method of producing ester salts of the kind described immediately preceding:

(0') An ester acid of a sulfoaromatic acid of the following structure:

RTSO3H said sulfoaryl fatty acid being an addition product of a monoethylenic higher fatty acid of the structure in which R is the monovalent hydrocarbon radical having a terminal methyl radical and connected with the ethyle'nic linkage, and R is the divalent hydrocarbon radical connecting the ethylenic linkage with the carboxyl radical; n being a whole number varying from 10 to 60; and with the further proviso that said ester acid is predominantly hydrophobe in character and the corresponding dibasic acid:

RSO3H is water-soluble and predominantly hydrophile; .and

(d) The method of preparing the last described ester acids.

The ester salts can be prepared most conveniently by either one of two procedures; oxypropylation of an'acid salt, or este'rification of the polybasic acid, followed by neutralization of the sulfonic groups. The ester acids, however, are most conveniently prepared as an intermeidate in the second step above described, i. e., by the esterication of the polybasic acid. For this reason the invention will be presented principally from a standpoint of the ester salts. The ester salts have been described and their production by oxy'propylation will be presented first, followed by a description of their production by esterification, along with a complete description of the intermediates.

More specifically then, the present invention is concerned with certain ester salts. These ester salts or derivatives of a dibasic acid contain one sulfonic acid radical and one carboxyl radical, in which the sulfonic acid radical is present in the form of a salt, and the carboxyl radical is present in the form of an ester. In some instances, the acid may be tribasic, due to the presence 'of 2 sulfonic radicals which form 2 salt groups.'

Ester salts of sulfo-aromatic fatty acids and particularly sulfoarylstearic acid are well known. The'me'thyl esters are invariably water-soluble, and this applies also to substantially other esters of low molal alcohol, such as the ethyl ester and butyl ester. Furthermore, the acids themselves, i. e., the unneutralized polybasic acids, are water-soluble, as is the case of the sodium, potassium, ammonium, or similar salts when all acid radicals appear in salt form. These materials, acids, the ester salts and the salts, are surface-active materials and serve'as Wetting agents, detergents, and emulsifying agents. They are completely water-soluble, as, for example, a 1% solution in Water of ordinary temperature (approximately 22.5 (2.). Such solution, when examined in an ordinary test tube (about 1 /2 centimeters or thereabouts in" depth) is perfectly clear and transparent. I:

A large group of such materials is described in U. S. Patent No. 2,302,070, dated November 17, 1942', to'Stirton et a1.

I have found that if, instead of producing the methyl ester, or ethyl ester, or propyl ester, or the butyl ester in the ester salt form, one prepares instead the ester of certain polypropylene glycols, one obtains the class of materials which have lost their water-solubility for all practical purposes, insofar that they may be water-insoluble or tend to momentarily suspend in Water during agitation, or at the most, give an opaque White suspension under the same conditions that the 'salts, free acids and ester salts where the alkyl radical of the ester' group is methyl or the like, are clearly water-soluble.

For convenience, the sulfoaryl fatty acid shown is depicted by the following formula:

for purpose of simplicity, as if it were a benzene radical, although obviously, it may be a substituted benzene 'ra'di- SOaNa The complete salt of the following structure is water-soluble:

SOslNa As a matter of fact, as previously pointed out, sodium in the last two formulae could be replaced by potassium, ammonium, or any other equivalent radical, such as the radical obtained by neutralization of triethanolamine:

Over and above this, the methyl ester in the form of the half salt (sodium salt for example) is also water-soluble. This may be depicted in the following manner:

S O Na Similarly, this would apply in almost every case when the ethyl radical happened to be replaced by the methyl radical, propyl radical, or butyl radical.

I have found that the half ester or ester salt of the following structure, completely loses its significant hydrophile properties, as far as such properties are controlling in the matter of wetting agents, emulsifying agents, detergents, and the like, as described, for example, in aforementioned U. S. Patent No. 2,302,070. The particular structure is SOaNa In the above formula the value of n may vary from to 60.

Such compounds, i. e., the half esters, or better still, ester salts, as also described, can be obtained by two different procedures, one involving oxypropylation and the other involving esterification.

The compounds prepared in the manner hereinafter described have utility for numerous purposes, and are particularly valuable as additives in the preparation of emulsions. This applies to the ester acids, as well as the ester salts. Extremely dilute emulsions, for instance, those in which the dispersed phase is less than two-tenths of a per cent, and usually less than one-tenth of a per cent, have been prepared without using an emulsifying agent. The majority of emulsions, however, are prepared by the use of an emulsifying agent, and thus, the emulsion system consists essentially of three ingredients. However, many technical emulsions actually have a fourth ingredient which may be an emulsifier of indifferent or unfreed effect, but is valuable, because it is a coupling agent, or mutual solvent. See The Composition and Structure of Technical Emulsions, I. H. Goodey, Royal Australian Chemical Inst. J. & Proc., 16, 1949, pp. 47-75.

' November 17, 1942, to Stirton et al.

The ester salts herein described, although having comparatively liimted or insignificant hydrophile property, in comparison with the products of the kind exemplified by those described in U. S. Patent No. 2,302,070, are particularly valuable as additives when emulsions are produced from the particular esters described in the patent immediately aforementioned. In other words, if one employs the products described in U. S. Patent No. 2,302,070, as emulsifying agents and they are particularly valuable for this purpose, one can obtain markedly better results in the preparation of some emulsions, if there is present some of the lesser hydrophile ester salts of the kind herein describd.

Another use for the products herein described is ,as an additive for lubricating oils, particularly petroleum lubrieating oils, to give added detersive qualities, and hence, other desirable characteristics. Needless to say, the compounds herein described having a terminal hydroxyl group can be reacted with various reagents, such as acids, imines, alkylene oxides other than propylene oxide, and the like, to give further derivatives of distinct value. When treated with one mole or several moles of styrene oxide (phenyl ethylene oxide), one obtains extremely valuable additives for various lubricating oils.

Sulfo-aromatic fatty acids and their salts have been known for approximately a half century. They were originally developed for fat-splitting and are sometimes referred to as fat-splitting reagents or Twitchell reagents.

Such sulfo-aromatic fatty acids and their salts can be obtained by various procedures, for instance, the procedure described by Twitchell in the original patents. Purely by way of illustration, reference is made to previously mentioned U. S. Patent No. 2,302,070, dated See also Industrial & Engineering Chemistry, volume 32, No. 8, page 1136 (1940). One general procedure involves the use of an unsaturated higher fatty acid and an aromatic material. Due to its availability, oleic acid is usually employed. The result of such reaction is either a sulfoaryl fatty acid or an aryl fatty acid, which can be subjected to sulfonation. Needless to say, fatty acids, and particularly fatty acids having less than 18 carbon atoms or more than 18 carbon atoms, can be employed.

By way of illustration, the following single example is included to indicate the method of preparing arylstearic acids or other analogous aryl fatty acids:

1.1 moles of oleic acid, 6.6 moles of xylene and 1.18 moles of anhydrous aluminum chloride are reacted for 4 hours at C. The mass is hydrolyzed in dilute hydrochloric acid, the solvent layer is separated and washed, and the excess of xylene is recovered by steam distillation. Steam distillation is continued, using superheated steam, to remove solid saturated fatty acids and to obtain a dry product. Yield 74%.

Attention is directed to the fact that the aforementioned article describes specifically the following arylstearic acids:

Phenylstear acids Tolylstearic acid Ethylphenylstearic acid Amylphenylstearic acid Xylylstearic acid Diethylphenylstearic acid Cymylstearic acid Diisopropylphenylstearic acid Pseudocumylstearic acid Tetrahydronaphthylstearic acid Chlorophenylstearic acid Ethoxyphenylstearic acid Phenoxyphenylstearic acid Xenylstearic acid The article also describes sulfonation of such acids so as to produce the comparable monosulfonic acid derivative, which is a polybasic acid having one carboxyl radical and one sulfonic acid radical. Such acids are often indicated by the prefix sulfo prior to the acid.

Thus, the sulfonation of the xylylstearic acid previously described is conducted in the following fashion:

The crude xylylstearic acid is sulfonated with 2.2 parts by weight of concentrated sulfuric acid for 1 hour at 100 C. The reaction mass is poured into water and the system extracted with ether. The ether solution is extracted with water, the aqueous solution neutralized with sodium hydroxide and evaporated. The dry residue is extracted with hot alcohol, the alcohol distilled from the alcoholic extract and sulfoxylylstearic acid isolated as the sodium salt. Analysis for sulfur=5.79%, calculated CzeH4205SNa2= 6.26

(See Example 1 of aforementioned U. S Patent No. 2,302,070.) Common examples of sulfoarylstearic acid are:

Sulfophenylstearic acid Sulfotolylstearic acid Sulfoethylphenylstearic acid Sulfoamylphenylstearic acid Sulfoxylylstearic acid Sulfodiethylphenylstearic acid Sulfocymylstearic acid Sulfodiisopropylphenylstearic acid Sulfopseudocumylstearic acid Sulfotetrahydronaphthylstearic acid Sulfochlorophenylstearic acid Sult'oethoxyphenylstearic acid Sulfophenoxyphenylstearic acid Sulfoxenylstearic acid Since the acidity of the sulfonic group is characteristic of that of a strong acid, there is no difliculty involved in neutralization to a suitable indicator, such as methyl orange, which indicates when a sulfonic group has been completely replaced by sodium, potassium, or the like. The monosodium or monopotassium salt can be prepared and dried in the customary manner. This yields a product which may be considered as half salt, half acid, or acid-salt, insofar that it contains both the typical salt structure and typical free carboxyl.

Examples then, of such sodium salts of sulfoarylstearic acid include the following:

Monosodium salt of sulfophenylstearic acid Monosodium salt of sulfotolystearic acid Monosodium salt of sulfoethylphenylstearic acid Monosodium salt of sulfoamylphenylstearic acid Monosodium salt of sulfooxylylstearic acid Monosodium salt of sulfodiethylphenylstearie acid Monosodium salt of sulfocymylstearic acid Monosodium salt of sulfodiisopropylphenylste aric acid Monosodium salt of sulfopseudocumylstearic acid Monosodium salt of sulfotetrahydronaphthylstearic acid Monosodium salt of sulfochlorophenylstearic acid Monosodium salt of sulfoethoxyphenylstearic acid Monosodium salt of sulfophenoxyphenylstearic acid Monosodium salt of sulfoxenylstearic acid It is to be emphasized again that the methyl esters of the above salts are perfectly water-soluble and have hydrophile properties characteristic of excellent wetting agents, emulsifying agents, detergents, .etc. This also applies to the unneutralized acids, as previously noted.

It has been pointed out previously that the here described compounds can be made in at least two difierent ways, i. e., involving either oxypropylation or esterificacation. For reasons which are apparent, in light of the subsequent text, I prefer to use esterification, but both procedures will be illustrated.

The sodium salts of sulfoaryl fatty acids of the kind previously described, invariably show at least some solubility in xylene. Potassium salt is more soluble than sodium salt. Salts of tertiary amines, such as tributylamine, are xylene-soluble to an even greater extent. As far as oxypropylation is concerned, it is immaterial whether the salt is soluble in xylene or not. The reason is that all that is necessary to use it, is to prepare a slurry of dry powder in xylene. Needless to say, any other suitable solvent that is non-reactive towards Pr p e Oxide and t a q l r d a can be emp o e In the particular procedure employed for preparation of the oxypropylated derivatives herein described, th autoclave was of conventional design. It was made of stainless steel and had a capacity of approximately one gallon and a working pressure of 1000 pounds gauge pressure. The autoclave was equipped with the conventional devices and openings, such as the variable stirrer operating at speeds from 50 R. P. M. to 500 R. P. M., thermometer Well and thermocouple for mechanical thermometer; emptying outlet; pressure gauge; manual vent line; charge hole for initial reactants; at least one connection for conducting the incoming alkylene oxide, such as ethylene oxide, to the bottom of the autoclave; along with suitable devices for both cooling and heating the autoclave, such as a cooling jacke t, and preferably, coils in addition thereto, with thejacket so arranged that it is suitable for heating with steam or cooling with water, and further equipped with electrical heating devices. Such autoclaves are, of course, in essence, small scale replicas of the usual conventional autoclave used in oxyalkylation procedures.

Continuous operation, or substantially continuous operation, is achieved by the use of a separate container to hold the alkylene oxide being employed, as propylene oxide'in the instant procedure. reage tainer consists essentially of a laboratory bomb having a capacity of about one-half gallon, or somewhat in excess thereof. This bomb was equipped, also, with an inlet for charging, and an outlet tube'goiug to thabottom of the container so as to permit discharging of alkylene oxide in the liquid phase to the autoclave. Other conventional equipment consists, of course, of the rupture disc, pressure gauge, sight feed glass, thermometer connection for nitrogen for pressuring bomb, etc. The bomb was placed on a scale during use and the connections between the bomb and the autoclave were flexible stainless hose or tubing, so that continuous weighings could be made without breaking or making any connections. This also applied to the nitrogen line, which was used to pressure the bomb reservoir. To the extent that it was required, any other usual conventional procedure or addition which provided greater safety was used, of course, such as safety glass, protective screens, etc.

In the following examples there are illustrated both intermediate and continuous oxypropylations, for the reason that intermediate oxypropylation is a convenient procedure by which exploratory oxypropylations can be made so as to determine when there has been a significant, and in fact, drastic change in water-solubility. In oxypropylation, there is a gradual change from characteristic hydrophile properties to properties which are dependent upon a comparatively limited or insignificant hydrophile effect. In esterification, the change :is complete at the end of the esterification operation, but needless to say, polypropylene glycols of various molecular weights may be employed, and thus even in the esterification procedure one can compare the eft'ec tof the increased molecular weight, due to an increased number of radicals resulting from propylene oxide 7 Il Example A Grams Sodium sulfoxylylstearic acid (purified acid sodiurn salt) 60 0 Xylene 600 Sodium methylate 8 Propylene oxide Q .350

The powdered sulfonate was placed in the autoclave with 600 grams of xylene and 8 grams of sodium methylate, as indicated. The autoclave was swept out with nitrogen and sealed. Stirring was started and heat applied. The temperature was allowed to rise to approximately 178 C. At this point propylene oxide was added to the extent of 350 grams. Notwithstanding the presence of the free hydroxyl radical, oxypropylation took place at a comparatively slow rate. The time required to combine the propylene oxide was 12 hours. The maximum temperature of operation was 177 C. Most of the time the temperature did not drop below 170 C. The maximum operating pressure was 165 pounds per square inch. The product at this stage, on a xylenefree basis, calculated as follows:

Per cent Sulfonate 63 Propylene oxide 37 and on a xylene-containing basis, calculated as follows:

Per cent Sulfonate 38.7 Propylene oxide 22.6 Xylene 38.7

Example B The autoclave was drained so as to permit 1000 grams of the reaction mass to stay in the autoclave. This was equivalent to 38.7 grams of sulfonate, 226 grams of propylene oxide, and 387 grams of xylene. The sodium methylate previously added was ignored for purpose of calculation. 6 grams of sodium methylate were added to the mixture and the autoclave flushed out with nitrogen as before and oxypropylation resumed. 375 grams of propylene oxide were added during this step. The time required was 4 /2 hours at a maximum temperature of 180 C., and a maximum pressure of 172 pounds per square inch. The composition corresponded to the following on a xylene-free basis.

Per cent Sulfonate 39.2 Propylene oxide 60.8

and on a xylene-containing basis it was calculated as follows:

Per cent Sulfonate 28.1 Propylene oxide 43.8 Xylene 28.1

Example C The autoclave was again drained so as to leave approximately 1000 grams of reaction mass, identified as Example B, preceding, in the autoclave. This corresponded to 281 grams of sulfonate, 438 grams of propylene oxide and 281 grams of xylene. The mixture was subjected to a third oxypropylation step, in which the time was 4 hours and the maximum temperature 175 C. The amount of propylene oxide added was 315 grams. The maximum pressure was 195 pounds per square inch. In the above procedure no sodium methylate was added. The product so obtained, on a xylene-free basis, corresponded to the following composition:

Per cent Sulfonate 27.2 Propylene oxide 72.8

On a xylene-containing basis, it was calculated as follows:

, Per cent Sulfonate 21.4 Propylene oxide 57.2 Xylene 21.4

This particular product began to show marked decrease inwater-solubility, when compared on a xylene-free basis 8 with the original sulfonate, and also with the two previous products, to wit, those exemplified by Examples A and B, preceding.

Example D The autoclave was again drained so as to leave 1000 grams of reaction mass identified as Example C, preceding, in the autoclave. This corresponded to 214 sulfonate, 572 grams of propylene oxide and 214 grams of xylene. The mixture was subjected to a third oxypropylation step, in which the time was 5 hours and a maximum temperature of 182 C. The amount of propylene oxide added was 290 grams. 3 grams of sodium methylate were also added. During this last step the maximum pressure was 185 pounds. The product so obtained, on a xylene-free basis, corresponded to the following composition:

Per cent Sulfonate 19.9 Proplene oxide 80.1

On a xylene-containing basis, it was calculated as follows:

Per cent Sulfonate 16.6 Propylene oxide 66.8 Xylene 16.6

This product showed marked decrease in water-solubility when compared on a xylene-free basis with the original sulfonate. A 1% solution, when shaken in a test tube, gave a white opaque dispersion showing marked reduction in hydrophile properties, as compared with the original sulfonate.

Per cent Sulfonate 16.6 Propylene oxide 83.7

On a xylene-containing basis, it was calculated as follows:

Per cent Sulfonate 14.3 Propylene oxide 71.4 Xylene 14.3

The product so obtained was of a pale, straw-colored tint, with distinct alkalinity due to the catalyst. When the xylene was removed and the product examined for solubility in the manner described above, it was even more insoluble than the preceding example. It showed a distinct tendency to oil out. This tendency was even greater when the alkalinity was eliminated by the use of hydrochloric acid. This alkalinity may be due, in part, to combined alkalinity, that is, the presence of sodium in combination with the carboxyl radical.

Example F Grams Sodium sulfoxlylstearic acid (purified acid sodium salt) 500 Xylene 500 Sodium methylate l6 Propylene oxide 2500 The procedure followed was the same as in Example A, preceding, except that the oxypropylation was a continuous process involving a single step. The time required was somewhat less than the interrupted procedures, being 14 /2 hours. The maximum temperature was 177 C., and the maximum pressure was 195 pounds per square inch. The final product was, of course, comparable in every respect to that identified as Example E, preceding.

As has been suggested previously, it is easier and preferable to derive the products herein specified by esterification, rather than oxypropylation. Whether derived by esterification or oxypropylation, one obtains a cogeneric mixture, rather than a single product. This particular phase of the situation will be considered at this point before turning to the procedure involving esterification.

Reference is made to the following formula which has appeared previously:

S OsNa In this formula the divalent radical (CsHeO)1t appears. Actually, when such products are obtained in the manner herein described, one does not obtain a single derivative, in which n has one and only one value, for instance, 14 or 15 or 16, or the like. Actually, one obtains a cogeneric mixture of closely related or touching homologues. These materials invariably have high molecular weights and cannot be separated from one another by any known procedure without decomposition. The properties of such mixture represent the contribution of the various individual members of the mixture. On a statistical basis, of course, it can be appropriately specified. For practical purposes, one need only consider the oxypropylation of a monohydric alcohol, because, in essence, this is substantially the mechanism involved. Even in such instances where one is concerned with a monohydric reactant, one cannot draw a single formula and say that by following such procedure, one can readily obtain 80% or 90% or 100% of such compound. However, in the case of at least monohydric initial reactants, one can readily draw the formulae of a large number of compounds which appear in some of the probable mixtures, or can be prepared as components and mixtures which are manufactured conventionally.

Simply by way of illustration, reference is made to the co-pending application of De Groote, Wirtel and Pettingill, Serial No. 109,791, filed August 11, 1949.

However, momentarily referring again to a monohydric initial reactant, it is obvious that if one selects any such simple hydroxylated compound and subjects such compound to oxyalkylation, such as oxyethylation, or oxypropylation, it becomes obvious that one is really producing a polymer of the alkylene oxide, except for the terminal group. This is particularly true where the amount of oxide added is comparatively large, for instance, 10, 20, 30, 40, or 50 units. If such a compound is subjected to oxyethylation so as to introduce units of ethylene oxide, it is well known that one does not obtain a single constituent, which, for the sake of convenience, may be indicated as RO(C2H4O)3OH. Instead, one obtains a cogeneric mixture of closely related homologues, in which the formula may be shown as the following: RO(C2H4O)11H, wherein n, as far as the statistical average goes, is 30, but the individual members present in significant amount may vary from instances where n has a value of 25, and perhaps less, to a point where I: may represent or more. Such mixture is, as stated, a cogeneric closely related series of touching homologous compounds. Considerable investigation has been made in regard itO the distribution curves for linear polymers. Attention is directed to the article entitled Fundamental Principles of Condensation Polymerization, :by :Paul J. Flory, which appeared in Chemical Reviews, volume 39, .No. .1, page 137.

Unfortunately, as has been pointed out by Flory and other investigators, there is no satisfactory method, based on either experimental or mathematical examination, of indicating the exact proportion of the various members of touching homologous series which appear in cogeneric condensation products of the kind described. This means that from the practical standpoint, i. e., the ability to describe how to make the product under consideration and how to repeat such production time after time without difiiculty, it is necessary to resort to some other method of description, or else consider the value of n in a formula such as as representing both individual constituents, in which n has a single definite value, and also with the understanding that n represents the average value based on completeness of reaction.

This may be illustrated as follows: Assume that in any particular example the molal ratio of the propylene oxide to the sulfonate is 15 to 1. Actually, one obtains products in which n probably varies from 10 to 20, perhaps even further. The average value, however, is 15, assuming, as previously stated, that the reaction is complete. The product described by the formula may be described also in terms of method of manufacture, but

insofar that a single hydroxyl only is involved, as differentiated from materials obtained by oxypropylation of polyhydric reactants, it appears more satisfactory to employ the customary formula type description, as long as the obvious limitations are completely understood.

The esterification of this sulfoaryl fatty acid is comparatively simple and repeated, for the reason that the sulfonic acid radical does not enter into the esterification procedure and the carboxyl radical esterifies rapidly, for the reason that the reactant per se is its own catalyst, i. e., is a sulfonic acid. The actual esterifications have been carried on in conventional apparatus; and on a laboratory scale I have used a glass resin pot, such as the kind described in U. 5. Patent No. 2,499,365, dated March 7, 1950, to De Groote and Keiser. Furthermore, I have used both the gallon size autoclave and the 1% gallon size autoclave of the kind previously described. When the autoclave was used as an esterification vessel, of course, it was connected to the condenser, so it could be used for refluxing, or in combination with the phase separating trap. The reaction was conducted until the amount of water evolved was equal to theoretical and until the reaction was completed, as indicated by some other test, such as the decrease in acid value, or decrease in hydroxyl value. After esterification, the product was neutralized by the addition of any of the usual basic materials, such as caustic soda, caustic potash, ammonia, various ethanolamines, cyclohexylamine, amylamiue, diamylamine, triamylamine, etc. Enough xylene was added, if required, so the mixture of acid (not the acid salt), and selected polypropyleneglycol refluxed at approximately C. The final product, with either the xylene present or xylene removed, was neutralized in the conventional manner. The final product, on a xylene-containing basis, represented amber-colored, viscous liquids or sticky solids, or sticky semi-solids. For

many purposes, the xylene may be permitted to stay in the final product. Needless to say, the xylene could be replaced by any other convenient solvent that would not interfere with any reaction involved, such as cymene, decalin, toluene, mesitylene, etc. The final product can, of course, be rendered solvent-free by distillation, and particularly vacuum distillation. The product can be bleached by use of various filtering chars, bleaching clays, or the like. The color is not objectionable for most technical purposes.

1 1 Purely by way of illustration, the following examples are included, although, as has been pointed out previously, this particular esterification is exceedingly rapid and satisfactory.

Example 1 468 grams of sulfoxylylstearic acid were placed in a resin pot of the kind previously described, along with polypropylene glycol 750. This is a polypropylene glycol of 750 average molecular weight. It is manufactured by the Dow Chemical Company. A similar product is manufactured by Carbide & Carbon Chemical Company. This applies to all subsequent polypropylene glycols herein mentioned, with the exception of polypropylene glycol 3000. To this mixture there were added 300 grams of xylene and the mixture stirred under a reflux condenser until it had refluxed for 3 hours, with a phase-separating trap employed to separate the water of reaction. The theoretical amount of water was eliminated in approximately 2 hours. Sufficient caustic soda solution by weight) was added slowly so as to neutralize the sulfonic acid radical only. Methyl orange was used as an indicator. The refluxing was then resumed long enough to eliminate water of solution which was present as a solvent for the caustic soda. If desired, xylene could be removed from the product in the manner previously indicated and the product could be bleached by clay or charcoal. The appearance of the product is the same, whether obtained in this manner or by oxypropylation.

Example 2 The same procedure was followed as in Example 1, except that the glycol was polypropylene glycol 1200, which is a polypropylene glycol of 1200 average molecular weight manufactured by Dow Chemical Company. 1200 grams of polypropylene glycol 1200 were used to replace 750 grams of polypropylene glycol 750 employed in Example 1, preceding. The amount of xylene employed was increased to 400 grams.

Example 3 The same procedure was followed as in Example 1, except that the glycol used was polypropylene glycol 2000, which is a polypropylene glycol of 2000 average molecular weight manufactured by Dow Chemical Company. 2000 grams of polypropylene glycol 2000 were used to replace 750 grams of polypropylene glycol 750 as in Example 1, preceding. The amount of xylene used was 650 grams.

Example 4 Polypropylene glycol 2750 was used. This polypropylene glycol has an avera e molecular weight of 2750 and is manufactured by Carbide & Carbon Chemical Co., New York city. 2750 grams of this glycol were used to replace 750 grams of polypropyleneglycol 750 employed in Example 1, preceding. The amount of xylene was increased to 850 grams.

Example 5 this polypropylene glycol 3000 were used to replace the 750 grams of polypropylene glycol 750 as used in Example l. The amount of xylene employed was increased to 900 grams.

Example 6 The same procedure was followed as in Example 1, ex-

12 cept that smaller amounts of reactants were employed and sultoamylphenylstearic acid was substituted for sulfoxylylstearic acid. 510 grams of sulfoamylphenylstearic acid were considered equivalent to 468 grams of sulfoxylylstearic acid. 51 grams of sulfoamylphenylstearic acid were mixed with grams of polypropylene glycol P750. To this mixture there were added grams of xylene. The esterification procedure was identical with that in Example 1, except that slightly more xylene was used purely as a convenience, because a smaller reaction vessel was employed.

Example 7 52.5 grams of sulfodiisopropylphenylstearic acid were substituted for 51 grams of sulfoamylphenylstearic acid in Example 6, preceding; otherwise, the same procedure was employed.

Example 8 49.4 grams of sulfotetrahydronaphthylstearic acid were substituted for 51 grams of sulfoamylphenylstearic acid as used in Example 6, preceding; otherwise, the same procedure was followed.

Example 9 54.4 grams of sulfophenoxyphenylstearic acid were substituted for 51 grams of sulfoamylphenylstearic acid as used in Example 6, preceding; otherwise, the same procedure was followed.

Example 10 Examples 6 to 9, inclusive, were repeated, with this change: 75 grams of polypropylene glycol 750 were replaced with grams of polypropylene glycol 1200.

Example 11 Examples 6 to 9, inclusive, were repeated, with this change: 75 grams of polypropylene glycol 750 were replaced by 200 grams of polypropylene glycol 2000. The amount of xylene employed was increased to grams.

Example 12 Examples 6 to 9, inclusive, were repeated, with this change: 75 grams of polypropylene glycol 750 were replaced by 275 grams of polypropylene glycol 2700. The amount of xylene employed was increased to grams.

Example 13 Examples 6 to 9, inclusive, were repeated, with this change: 300 grams of polypropylene glycol 3000 were used to replace the 75 grams of polypropylene glycol 750, and xylene was increased to grams.

Attention is directed to the fact that the above examples illustrate the ester acids and the method of making the same which are an inherent part of the instant invention.

The half-esters obtained in the manner above described have been neutralized with various bases. The sodium, potassium, and ammonium salts invariably show a lack of water solubility previously noted. They are predominantly hydrophobe in character, whereas, the corresponding methyl ester, for example, is predominantly hydrophile in character. Hydrophobe character can, of course, be increased by neutralization by materials, such as cyclohexylamine, amylamine, dibutylamine, triethanolamine, etc. Hydroxylated amines, such as the ethanolamines, particularly triethanolamines and the propanolamines, can be employed. The use of triethanolamine and particularly oxyethylated triethanolamine, sometimes produce products which show rather peculiar solubilit effects.

As has been pointed out previously, esterification can be accomplished by simply mixing the reactants in absence of xylene or any other solvent, holding the temperature to approximately 175 to 200 C., and preferably passing dried nitrogen through the mixture until esterification is complete, or substantially complete.

In light of what has been said, it is apparent that the 13 product itself need not be used in the form of a sodium salt, but may be in the form of a potassium salt, calcium salt, magnesium salt, amine salt, etc. This may be shown by the following formula:

S ;.Cation However, since the sulfoaryl fatty acids can be obtained from a variety of aromatic material, rather than using the conventional phenol radical, as appears in the above formula, it appears desirable to rewrite the formula thus:

in which R represents the monocyclic or polycyclic aryl group or aryloxyaryl group, or the alkylated aryl group. For convenience, this aryl group may, of course, have chlorine, as illustrated by previous examples.

It was pointed out in the early part of the specification that the invention was concerned also with said esters as well as ester salts. It is to be noted that in the subject-matter preceding there has been a very complete and adequate description of the manufacture of the ester acids which subsequently are converted into said salts by neutralization.

Reference is made again to U. S. Patent No. 2,302,070. This particular patent points out that the polybasic acids, such as OsH SULFOXENYLSTEARIC ACID are also used as wetting agents, surface-active material's, emulsifiers, etc. The hydrophobic eifect contributed by the radical obtained by oxypropylation or its equivalent is also significant in the structure of the ester acids. In other words, the dibasic acid of the structure:

"-sonl is water-soluble and predominantly hydrophile. On the other hand, the corresponding acid ester of the structure:

SO3H

is predominantly hydrophile in character.

Stated another way, the same solubility test employed previously to distinguish the comparative insolubility, or at the most, dispersibility of the present invention from the water-soluble products of the kind described in aforementioned U. S. Patent No. 2,302,070, applies in the case of the acid esters just as effectively as in the case of the ester salts. The same test can be used in every resin.

The acid esters also are valuable as coupling agents or emulsion additives, and particularly when emulsions are made by use of a water-soluble dibasic acid of the kind described. Over and above this, such acid esters can be employed for a variety of purposes to produce more complicated derivatives, such as the salts described elsewhere and also other derivatives involving further alteration 'of the sulfonic acid radical.

1 4 Having thus described my invention, what I claim as new and desire to secure by Letters Patent is:

1. The ester salt of a sulfoaryl fatty acid of the following structure:

in which R" is an aryl radical having not more than 25 carbon atoms; said sulfoaryl fatty acid being an addition product of a monoethylenic higher fatty acid of the structure:

in which R is the monovalent hydrocarbon radical having a terminal methyl radical and connected with the ethylenic linkage, and R is the divalent hydrocarbon radical connecting the ethylenic linkage with the carboxyl radical; n being a whole number varying from to 60; and with the further proviso that the Sodium salt is predominantly hydrophobe in character, and the corresponding methyl ester of the sodium salt is water-soluble and predominantly hydrophile.

2. The ester salt of a sulfoaryl fatty acid of the following structure:

SOa.Na

in Which R is an aryl radical having not more than carbon atoms; said sulfoaryl fatty acid being an addition product of a monoethylenic higher fatty acid of the structure in which R is the monovalent hydrocarbon radical having a terminal methyl radical and connected with the ethylenic linkage, and R is the divalent hydrocarbon radical connecting the ethylenic linkage with the carboxyl radical; n being a whole number varying from 10 to and with the further proviso that said sodium salt is predominantly hydrophobe in character and the corresponding methyl ester of the sodium salt is monocyclic, the fatty acid radical contains 18 carbon atoms, and the value of n is approximately 20.

7. The product of claim 2, wherein the aryl radical is monocyclic, the fatty acid radical contains 18 carbon atoms, and the value of n is approximately 35.

8. The product of claim 2, wherein the aryl radical is monocyclic, the fatty acid radical contains 18 carbon atoms, and the value of n is approximately 46.

9. The product of claim 2, wherein the aryl radical is monocyclic, the fatty acid radical contains 18 carbon atoms, and the value of n is approximately 52.

10. The process of preparing an ester salt of a sulfoaryl fatty acid of the following structure:

in which R" is an aryl radical having not more than carbon atoms; said sulfoaryl fatty acid being an addition product of a monoethylenic higher fatty acid of the structure in which R is the monovalent hydrocarbon radical having a terminal methyl radical and connected with the ethylenic linkage, and R is the divalent hydrocarbon radical connecting the ethylenic linkage with the carboxyl radical; n being a whole number varying from 10 to 60; and with the further proviso that the sodium salt is predominantly hydrophobe in character, and the corresponding methyl ester of the sodium salt is Water-soluble and predominantly hydrophile; by the neutralization of the acid ester obtained by esterifying a sulfoaryl fatty acid of the following structure:

in which R and R have their prior significance, with a polypropylene glycol of the following structure:

in which n has its prior significance.

11. The process of preparing an ester salt of a sulfoaryl fatty acid of the following structure:

in which R" is an aryl radical having not more than 25 carbon atoms; said sulfoaryl fatty acid being an addition product of a monoethylenic higher fatty acid of the is water-soluble and predominantly hydrophile; said ester salt being obtained by the neutralization of the acid ester obtained by esterifying a sulfoaryl fatty acid of the following structure:

in which R and R have their prior significance, with a polypropylene glycol of the following structure:

in which n has its prior significance.

12. The process of claim 11, wherein the aryl radical is monocyclic.

13. The process of claim 11, wherein the aryl radicalis rnonocyclic, and the fatty acid radical contains 18 carbon atoms.

14. The process of claim 11, wherein the aryl radical is rnonocyclic, the fatty acid radical contains 18 carbon atoms, and the value of n is approximately l2.

15. The process of claim 11, wherein the aryl radical is rnonocyclic, the fatty acid radical contains 18 carbon atoms, and the value of n is approximately 2O.

16. The process of claim 11, wherein the aryl radical is rnonocyclic, the fatty acid radical contains 18 carbon atoms, and the value of n is approximately 35.

17. The process of claim 11, wherein the aryl radical is rnonocyclic, the fatty acid radical contains 18 carbon atoms, and the value of n is approximately 46.

18. The process of claim 11, wherein the aryl radical is rnonocyclic, the fatty acid radical contains 18 carbon atoms, and the value of n is approximately 52.

19. The ester acid of a sulfoaromatic acid of the following structure:

in which R" is an aryl radical having not more than 25 carbon atoms; said sulfoaryl fatty acid being an addition product of a monoethylenic higher fatty acid of the structure in which R is a monovalent hydrocarbon radical having a terminal methyl radical and connected with the ethylenic linkage, and R is the divalent hydrocarbon radical conmeeting the ethylenic linkage with the carboxyl radical; n. being a whole number varying from 10 to 60; and with the further proviso that said ester acid is predominantly hydrophobe in character and the corresponding dibasic acid "-SO3H H l R-C-CRCOOH is water-soluble and predominantly hydrophile.

20. The product of claim 19, wherein the aryl radical is monocyclic.

21. The product of claim 19, wherein the aryl radical is rnonocyclic, and the fatty acid radical contains 18 carbon atoms.

22. The product of claim 19, wherein the aryl radical is rnonocyclic, the fatty acid radical contains 18 carbon atoms, and the value of n is approximately 12.

23. The product of claim 19, wherein the aryl radical is rnonocyclic, the fatty acid radical contains 18 carbon atoms, and the value of n is approximately 20.

24. The product of claim 19, wherein the aryl radical is rnonocyclic, the fatty acid radical contains 18 carbon atoms, and the value of n is approximately 35.

25. The product of claim 19, wherein the aryl radical is rnonocyclic, the fatty acid radical contains 18 carbon atoms, and the value of n is approximately 46.

26. The product of claim 19, wherein the aryl radical is rnonocyclic, the fatty acid radical contains 18 carbon atoms, and the value of n is approximately 52.

27. The process of preparing an ester acid of a sulfoaryl fatty acid of the following structure:

in which R is the monovalent hydrocarbon radical havis water-soluble and predominantly hydrophile; said ester acid being obtained by the esterification of a sulfoaryl fatty acid of the following structure:

R-SO3H H R--C RCOOH in which R and R have their prior significance, with a polypropylene glycol of the following structure:

HO(C3H60)1IH in which n has its prior significance.

28. The process of claim 27, wherein the aryl radical is monocyclic.

29. The process of claim 27, wherein the aryl radical is monocyclic, and the fatty acid radical contains 18 carbon atoms.

30. The process of claim 27, wherein the aryl radical is monocyclic, the fatty acid radical contains 18 carbon atoms, and the value of n is approximately 12.

31. The process of claim 27, wherein the aryl radical is monocyclic, the fatty acid radical contains 18 carbon atoms, and the value of n is approximately 20.

32. The process of claim 27, wherein the aryl radical is monocyclic, the fatty acid radical contains 18 carbon atoms, and the value of n is approximately 35.

33. The process of claim 27, wherein the aryl radical is monocyclic, the fatty acid radical contains 18 carbon atoms, and the value of n is approximately 46.

References Cited in the file of this patent UNITED STATES PATENTS Stirton et al. Nov. 17, 1942 De Groote et al Mar. 27, 1945 

1. THE ESTER SALT OF A SULFOARYL FATTY ACID OF THE FOLLOWING STRUCTURE: 